bluetooth: don't use bitmaps for random flag accesses

The bluetooth code uses our bitmap infrastructure for the two bits (!)
of connection setup flags, and in the process causes odd problems when
it converts between a bitmap and just the regular values of said bits.

It's completely pointless to do things like bitmap_to_arr32() to convert
a bitmap into a u32.  It shoudln't have been a bitmap in the first
place.  The reason to use bitmaps is if you have arbitrary number of
bits you want to manage (not two!), or if you rely on the atomicity
guarantees of the bitmap setting and clearing.

The code could use an "atomic_t" and use "atomic_or/andnot()" to set and
clear the bit values, but considering that it then copies the bitmaps
around with "bitmap_to_arr32()" and friends, there clearly cannot be a
lot of atomicity requirements.

So just use a regular integer.

In the process, this avoids the warnings about erroneous use of
bitmap_from_u64() which were triggered on 32-bit architectures when
conversion from a u64 would access two words (and, surprise, surprise,
only one word is needed - and indeed overkill - for a 2-bit bitmap).

That was always problematic, but the compiler seems to notice it and
warn about the invalid pattern only after commit 0a97953fd221 ("lib: add
bitmap_{from,to}_arr64") changed the exact implementation details of
'bitmap_from_u64()', as reported by Sudip Mukherjee and Stephen Rothwell.

Fixes: fe92ee6425a2 ("Bluetooth: hci_core: Rework hci_conn_params flags")
Link: https://lore.kernel.org/all/YpyJ9qTNHJzz0FHY@debian/
Link: https://lore.kernel.org/all/20220606080631.0c3014f2@canb.auug.org.au/
Link: https://lore.kernel.org/all/20220605162537.1604762-1-yury.norov@gmail.com/
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reported-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Reviewed-by: Yury Norov <yury.norov@gmail.com>
Cc: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Cc: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 14 insertions, 23 deletions

diff --git a/net/bluetooth/mgmt.c b/net/bluetooth/mgmt.c
index 74937a834648..ae758ab1b558 100644
--- a/net/bluetooth/mgmt.c
+++ b/net/bluetooth/mgmt.c
@@ -4013,10 +4013,11 @@ static int exp_ll_privacy_feature_changed(bool enabled, struct hci_dev *hdev,
 	memcpy(ev.uuid, rpa_resolution_uuid, 16);
 	ev.flags = cpu_to_le32((enabled ? BIT(0) : 0) | BIT(1));
 
+	// Do we need to be atomic with the conn_flags?
 	if (enabled && privacy_mode_capable(hdev))
-		set_bit(HCI_CONN_FLAG_DEVICE_PRIVACY, hdev->conn_flags);
+		hdev->conn_flags |= HCI_CONN_FLAG_DEVICE_PRIVACY;
 	else
-		clear_bit(HCI_CONN_FLAG_DEVICE_PRIVACY, hdev->conn_flags);
+		hdev->conn_flags &= ~HCI_CONN_FLAG_DEVICE_PRIVACY;
 
 	return mgmt_limited_event(MGMT_EV_EXP_FEATURE_CHANGED, hdev,
 				  &ev, sizeof(ev),
@@ -4435,8 +4436,7 @@ static int get_device_flags(struct sock *sk, struct hci_dev *hdev, void *data,
 
 	hci_dev_lock(hdev);
 
-	bitmap_to_arr32(&supported_flags, hdev->conn_flags,
-			__HCI_CONN_NUM_FLAGS);
+	supported_flags = hdev->conn_flags;
 
 	memset(&rp, 0, sizeof(rp));
 
@@ -4447,8 +4447,7 @@ static int get_device_flags(struct sock *sk, struct hci_dev *hdev, void *data,
 		if (!br_params)
 			goto done;
 
-		bitmap_to_arr32(&current_flags, br_params->flags,
-				__HCI_CONN_NUM_FLAGS);
+		current_flags = br_params->flags;
 	} else {
 		params = hci_conn_params_lookup(hdev, &cp->addr.bdaddr,
 						le_addr_type(cp->addr.type));
@@ -4456,8 +4455,7 @@ static int get_device_flags(struct sock *sk, struct hci_dev *hdev, void *data,
 		if (!params)
 			goto done;
 
-		bitmap_to_arr32(&current_flags, params->flags,
-				__HCI_CONN_NUM_FLAGS);
+		current_flags = params->flags;
 	}
 
 	bacpy(&rp.addr.bdaddr, &cp->addr.bdaddr);
@@ -4502,8 +4500,8 @@ static int set_device_flags(struct sock *sk, struct hci_dev *hdev, void *data,
 		   &cp->addr.bdaddr, cp->addr.type,
 		   __le32_to_cpu(current_flags));
 
-	bitmap_to_arr32(&supported_flags, hdev->conn_flags,
-			__HCI_CONN_NUM_FLAGS);
+	// We should take hci_dev_lock() early, I think.. conn_flags can change
+	supported_flags = hdev->conn_flags;
 
 	if ((supported_flags | current_flags) != supported_flags) {
 		bt_dev_warn(hdev, "Bad flag given (0x%x) vs supported (0x%0x)",
@@ -4519,7 +4517,7 @@ static int set_device_flags(struct sock *sk, struct hci_dev *hdev, void *data,
 							      cp->addr.type);
 
 		if (br_params) {
-			bitmap_from_u64(br_params->flags, current_flags);
+			br_params->flags = current_flags;
 			status = MGMT_STATUS_SUCCESS;
 		} else {
 			bt_dev_warn(hdev, "No such BR/EDR device %pMR (0x%x)",
@@ -4529,15 +4527,11 @@ static int set_device_flags(struct sock *sk, struct hci_dev *hdev, void *data,
 		params = hci_conn_params_lookup(hdev, &cp->addr.bdaddr,
 						le_addr_type(cp->addr.type));
 		if (params) {
-			DECLARE_BITMAP(flags, __HCI_CONN_NUM_FLAGS);
-
-			bitmap_from_u64(flags, current_flags);
-
 			/* Devices using RPAs can only be programmed in the
 			 * acceptlist LL Privacy has been enable otherwise they
 			 * cannot mark HCI_CONN_FLAG_REMOTE_WAKEUP.
 			 */
-			if (test_bit(HCI_CONN_FLAG_REMOTE_WAKEUP, flags) &&
+			if ((current_flags & HCI_CONN_FLAG_REMOTE_WAKEUP) &&
 			    !use_ll_privacy(hdev) &&
 			    hci_find_irk_by_addr(hdev, &params->addr,
 						 params->addr_type)) {
@@ -4546,14 +4540,13 @@ static int set_device_flags(struct sock *sk, struct hci_dev *hdev, void *data,
 				goto unlock;
 			}
 
-			bitmap_from_u64(params->flags, current_flags);
+			params->flags = current_flags;
 			status = MGMT_STATUS_SUCCESS;
 
 			/* Update passive scan if HCI_CONN_FLAG_DEVICE_PRIVACY
 			 * has been set.
 			 */
-			if (test_bit(HCI_CONN_FLAG_DEVICE_PRIVACY,
-				     params->flags))
+			if (params->flags & HCI_CONN_FLAG_DEVICE_PRIVACY)
 				hci_update_passive_scan(hdev);
 		} else {
 			bt_dev_warn(hdev, "No such LE device %pMR (0x%x)",
@@ -7154,8 +7147,7 @@ static int add_device(struct sock *sk, struct hci_dev *hdev,
 		params = hci_conn_params_lookup(hdev, &cp->addr.bdaddr,
 						addr_type);
 		if (params)
-			bitmap_to_arr32(&current_flags, params->flags,
-					__HCI_CONN_NUM_FLAGS);
+			current_flags = params->flags;
 	}
 
 	err = hci_cmd_sync_queue(hdev, add_device_sync, NULL, NULL);
@@ -7164,8 +7156,7 @@ static int add_device(struct sock *sk, struct hci_dev *hdev,
 
 added:
 	device_added(sk, hdev, &cp->addr.bdaddr, cp->addr.type, cp->action);
-	bitmap_to_arr32(&supported_flags, hdev->conn_flags,
-			__HCI_CONN_NUM_FLAGS);
+	supported_flags = hdev->conn_flags;
 	device_flags_changed(NULL, hdev, &cp->addr.bdaddr, cp->addr.type,
 			     supported_flags, current_flags);